The invention relates to a clamping collar.
Such a collar can be used to connect pipes, in particular in the automobile industry or in the aircraft industry (e.g. to connect pipes of the exhaust system or of the system for depolluting combustion gases).
More particularly, the invention relates to a clamping collar of the type comprising:                a belt having two free ends, at least one of said free ends being curved back to form a loop, said loop being defined by an outer belt portion and by an underlying inner belt portion; and        a tightening system suitable for co-operating with said loop so as to tighten said belt.        
Generally, both of the free ends of said belt are curved back so as to form respective loops, and said tightening system makes it possible bring said loops closer together for tightening said belt.
A collar of this type is described in Document FR 2 522 086. That collar has a tightening system with two semi-cylindrical retaining pieces that are received inside respective ones of the two loops of the collar. Such retaining pieces can be referred to as “blocks” or as “gudgeons”.
The first block is provided with a tapped through hole and the second block is provided with a smooth through hole. The tightening system further comprises a screw having a threaded shank and a screw head. Each loop of the collar is provided two openings that are in register with each other so that the shank of the screw passes through each of the two loops. In addition, the shank of the screw passes freely through the smooth hole and engages in the tapped hole. While the screw is being screwed into the first block, the screw head comes into engagement with the second block which then pushes against the inner belt portion of one loop, while the first block pushes against the inner belt portion of the other loop. The collar is thus tightened by bringing said loops closer together.